Using the GNU Privacy Guard: GPG Esoteric Options

Next: Deprecated Options, Previous: Compliance Options, Up: GPG Options [Contents][Index]

#### 3.2.6 Doing things one usually doesn’t want to do.

`-n`
`--dry-run`

  Don’t make any changes (this is not completely implemented).

`--list-only`

  Changes the behaviour of some commands. This is like `--dry-run` but different in some cases. The semantic of this command may be extended in the future. Currently it only skips the actual decryption pass and therefore enables a fast listing of the encryption keys.

`-i`
`--interactive`

  Prompt before overwriting any files.

`--debug-level level`

  Select the debug level for investigating problems. level may be a numeric value or by a keyword:

  `none`

    No debugging at all. A value of less than 1 may be used instead of the keyword.

  `basic`

    Some basic debug messages. A value between 1 and 2 may be used instead of the keyword.

  `advanced`

    More verbose debug messages. A value between 3 and 5 may be used instead of the keyword.

  `expert`

    Even more detailed messages. A value between 6 and 8 may be used instead of the keyword.

  `guru`

    All of the debug messages you can get. A value greater than 8 may be used instead of the keyword. The creation of hash tracing files is only enabled if the keyword is used.

  How these messages are mapped to the actual debugging flags is not specified and may change with newer releases of this program. They are however carefully selected to best aid in debugging.

`--debug flags`

  Set debugging flags. All flags are or-ed and flags may be given in C syntax (e.g. 0x0042).

`--debug-all`

  Set all useful debugging flags.

`--faked-system-time epoch`

  This option is only useful for testing; it sets the system time back or forth to epoch which is the number of seconds elapsed since the year 1970. Alternatively epoch may be given as a full ISO time string (e.g. "20070924T154812").

`--enable-progress-filter`

  Enable certain PROGRESS status outputs. This option allows frontends to display a progress indicator while gpg is processing larger files. There is a slight performance overhead using it.

`--status-fd `n``

  Write special status strings to the file descriptor `n`. See the file DETAILS in the documentation for a listing of them.

`--status-file `file``

  Same as `--status-fd`, except the status data is written to file `file`.

`--logger-fd `n``

  Write log output to file descriptor `n` and not to STDERR.

`--log-file `file``
`--logger-file `file``

  Same as `--logger-fd`, except the logger data is written to file `file`. Note that `--log-file` is only implemented for GnuPG-2.

`--attribute-fd `n``

  Write attribute subpackets to the file descriptor `n`. This is most useful for use with `--status-fd`, since the status messages are needed to separate out the various subpackets from the stream delivered to the file descriptor.

`--attribute-file `file``

  Same as `--attribute-fd`, except the attribute data is written to file `file`.

`--comment `string``
`--no-comments`

  Use `string` as a comment string in clear text signatures and ASCII armored messages or keys (see `--armor`). The default behavior is not to use a comment string. `--comment` may be repeated multiple times to get multiple comment strings. `--no-comments` removes all comments. It is a good idea to keep the length of a single comment below 60 characters to avoid problems with mail programs wrapping such lines. Note that comment lines, like all other header lines, are not protected by the signature.

`--emit-version`
`--no-emit-version`

  Force inclusion of the version string in ASCII armored output. If given once only the name of the program and the major number is emitted (default), given twice the minor is also emitted, given triple the micro is added, and given quad an operating system identification is also emitted. `--no-emit-version` disables the version line.

`--sig-notation `name=value``
`--cert-notation `name=value``
`-N, --set-notation `name=value``

  Put the name value pair into the signature as notation data. `name` must consist only of printable characters or spaces, and must contain a ’@’ character in the form keyname@domain.example.com (substituting the appropriate keyname and domain name, of course). This is to help prevent pollution of the IETF reserved notation namespace. The `--expert` flag overrides the ’@’ check. `value` may be any printable string; it will be encoded in UTF8, so you should check that your `--display-charset` is set correctly. If you prefix `name` with an exclamation mark (!), the notation data will be flagged as critical (rfc4880:5.2.3.16). `--sig-notation` sets a notation for data signatures. `--cert-notation` sets a notation for key signatures (certifications). `--set-notation` sets both.

  There are special codes that may be used in notation names. "%k" will be expanded into the key ID of the key being signed, "%K" into the long key ID of the key being signed, "%f" into the fingerprint of the key being signed, "%s" into the key ID of the key making the signature, "%S" into the long key ID of the key making the signature, "%g" into the fingerprint of the key making the signature (which might be a subkey), "%p" into the fingerprint of the primary key of the key making the signature, "%c" into the signature count from the OpenPGP smartcard, and "%%" results in a single "%". %k, %K, and %f are only meaningful when making a key signature (certification), and %c is only meaningful when using the OpenPGP smartcard.

`--sig-policy-url `string``
`--cert-policy-url `string``
`--set-policy-url `string``

  Use `string` as a Policy URL for signatures (rfc4880:5.2.3.20). If you prefix it with an exclamation mark (!), the policy URL packet will be flagged as critical. `--sig-policy-url` sets a policy url for data signatures. `--cert-policy-url` sets a policy url for key signatures (certifications). `--set-policy-url` sets both.

  The same %-expandos used for notation data are available here as well.

`--sig-keyserver-url `string``

  Use `string` as a preferred keyserver URL for data signatures. If you prefix it with an exclamation mark (!), the keyserver URL packet will be flagged as critical.

  The same %-expandos used for notation data are available here as well.

`--set-filename `string``

  Use `string` as the filename which is stored inside messages. This overrides the default, which is to use the actual filename of the file being encrypted.

`--for-your-eyes-only`
`--no-for-your-eyes-only`

  Set the ‘for your eyes only’ flag in the message. This causes GnuPG to refuse to save the file unless the `--output` option is given, and PGP to use a "secure viewer" with a claimed Tempest-resistant font to display the message. This option overrides `--set-filename`. `--no-for-your-eyes-only` disables this option.

`--use-embedded-filename`
`--no-use-embedded-filename`

  Try to create a file with a name as embedded in the data. This can be a dangerous option as it allows to overwrite files. Defaults to no.

`--cipher-algo `name``

  Use `name` as cipher algorithm. Running the program with the command `--version` yields a list of supported algorithms. If this is not used the cipher algorithm is selected from the preferences stored with the key. In general, you do not want to use this option as it allows you to violate the OpenPGP standard. `--personal-cipher-preferences` is the safe way to accomplish the same thing.

`--digest-algo `name``

  Use `name` as the message digest algorithm. Running the program with the command `--version` yields a list of supported algorithms. In general, you do not want to use this option as it allows you to violate the OpenPGP standard. `--personal-digest-preferences` is the safe way to accomplish the same thing.

`--compress-algo `name``

  Use compression algorithm `name`. "zlib" is RFC-1950 ZLIB compression. "zip" is RFC-1951 ZIP compression which is used by PGP. "bzip2" is a more modern compression scheme that can compress some things better than zip or zlib, but at the cost of more memory used during compression and decompression. "uncompressed" or "none" disables compression. If this option is not used, the default behavior is to examine the recipient key preferences to see which algorithms the recipient supports. If all else fails, ZIP is used for maximum compatibility.

  ZLIB may give better compression results than ZIP, as the compression window size is not limited to 8k. BZIP2 may give even better compression results than that, but will use a significantly larger amount of memory while compressing and decompressing. This may be significant in low memory situations. Note, however, that PGP (all versions) only supports ZIP compression. Using any algorithm other than ZIP or "none" will make the message unreadable with PGP. In general, you do not want to use this option as it allows you to violate the OpenPGP standard. `--personal-compress-preferences` is the safe way to accomplish the same thing.

`--cert-digest-algo `name``

  Use `name` as the message digest algorithm used when signing a key. Running the program with the command `--version` yields a list of supported algorithms. Be aware that if you choose an algorithm that GnuPG supports but other OpenPGP implementations do not, then some users will not be able to use the key signatures you make, or quite possibly your entire key.

`--disable-cipher-algo `name``

  Never allow the use of `name` as cipher algorithm. The given name will not be checked so that a later loaded algorithm will still get disabled.

`--disable-pubkey-algo `name``

  Never allow the use of `name` as public key algorithm. The given name will not be checked so that a later loaded algorithm will still get disabled.

`--throw-keyids`
`--no-throw-keyids`

  Do not put the recipient key IDs into encrypted messages. This helps to hide the receivers of the message and is a limited countermeasure against traffic analysis.1 On the receiving side, it may slow down the decryption process because all available secret keys must be tried. `--no-throw-keyids` disables this option. This option is essentially the same as using `--hidden-recipient` for all recipients.

`--not-dash-escaped`

  This option changes the behavior of cleartext signatures so that they can be used for patch files. You should not send such an armored file via email because all spaces and line endings are hashed too. You can not use this option for data which has 5 dashes at the beginning of a line, patch files don’t have this. A special armor header line tells GnuPG about this cleartext signature option.

`--escape-from-lines`
`--no-escape-from-lines`

  Because some mailers change lines starting with "From " to ">From " it is good to handle such lines in a special way when creating cleartext signatures to prevent the mail system from breaking the signature. Note that all other PGP versions do it this way too. Enabled by default. `--no-escape-from-lines` disables this option.

`--passphrase-repeat `n``

  Specify how many times `gpg2` will request a new passphrase be repeated. This is useful for helping memorize a passphrase. Defaults to 1 repetition.

`--passphrase-fd `n``

  Read the passphrase from file descriptor `n`. Only the first line will be read from file descriptor `n`. If you use 0 for `n`, the passphrase will be read from STDIN. This can only be used if only one passphrase is supplied. Note that this passphrase is only used if the option `--batch` has also been given. This is different from `gpg`.

`--passphrase-file `file``

  Read the passphrase from file `file`. Only the first line will be read from file `file`. This can only be used if only one passphrase is supplied. Obviously, a passphrase stored in a file is of questionable security if other users can read this file. Don’t use this option if you can avoid it. Note that this passphrase is only used if the option `--batch` has also been given. This is different from `gpg`.

`--passphrase `string``

  Use `string` as the passphrase. This can only be used if only one passphrase is supplied. Obviously, this is of very questionable security on a multi-user system. Don’t use this option if you can avoid it. Note that this passphrase is only used if the option `--batch` has also been given. This is different from `gpg`.

`--command-fd `n``

  This is a replacement for the deprecated shared-memory IPC mode. If this option is enabled, user input on questions is not expected from the TTY but from the given file descriptor. It should be used together with `--status-fd`. See the file doc/DETAILS in the source distribution for details on how to use it.

`--command-file `file``

  Same as `--command-fd`, except the commands are read out of file `file`

`--allow-non-selfsigned-uid`
`--no-allow-non-selfsigned-uid`

  Allow the import and use of keys with user IDs which are not self-signed. This is not recommended, as a non self-signed user ID is trivial to forge. `--no-allow-non-selfsigned-uid` disables.

`--allow-freeform-uid`

  Disable all checks on the form of the user ID while generating a new one. This option should only be used in very special environments as it does not ensure the de-facto standard format of user IDs.

`--ignore-time-conflict`

  GnuPG normally checks that the timestamps associated with keys and signatures have plausible values. However, sometimes a signature seems to be older than the key due to clock problems. This option makes these checks just a warning. See also `--ignore-valid-from` for timestamp issues on subkeys.

`--ignore-valid-from`

  GnuPG normally does not select and use subkeys created in the future. This option allows the use of such keys and thus exhibits the pre-1.0.7 behaviour. You should not use this option unless there is some clock problem. See also `--ignore-time-conflict` for timestamp issues with signatures.

`--ignore-crc-error`

  The ASCII armor used by OpenPGP is protected by a CRC checksum against transmission errors. Occasionally the CRC gets mangled somewhere on the transmission channel but the actual content (which is protected by the OpenPGP protocol anyway) is still okay. This option allows GnuPG to ignore CRC errors.

`--ignore-mdc-error`

  This option changes a MDC integrity protection failure into a warning. This can be useful if a message is partially corrupt, but it is necessary to get as much data as possible out of the corrupt message. However, be aware that a MDC protection failure may also mean that the message was tampered with intentionally by an attacker.

`--allow-weak-digest-algos`

  Signatures made with the broken MD5 algorithm are normally rejected with an “invalid digest algorithm” message. This option allows the verification of signatures made with such weak algorithms.

`--no-default-keyring`

  Do not add the default keyrings to the list of keyrings. Note that GnuPG will not operate without any keyrings, so if you use this option and do not provide alternate keyrings via `--keyring` or `--secret-keyring`, then GnuPG will still use the default public or secret keyrings.

`--skip-verify`

  Skip the signature verification step. This may be used to make the decryption faster if the signature verification is not needed.

`--with-key-data`

  Print key listings delimited by colons (like `--with-colons`) and print the public key data.

`--fast-list-mode`

  Changes the output of the list commands to work faster; this is achieved by leaving some parts empty. Some applications don’t need the user ID and the trust information given in the listings. By using this options they can get a faster listing. The exact behaviour of this option may change in future versions. If you are missing some information, don’t use this option.

`--no-literal`

  This is not for normal use. Use the source to see for what it might be useful.

`--set-filesize`

  This is not for normal use. Use the source to see for what it might be useful.

`--show-session-key`

  Display the session key used for one message. See `--override-session-key` for the counterpart of this option.

  We think that Key Escrow is a Bad Thing; however the user should have the freedom to decide whether to go to prison or to reveal the content of one specific message without compromising all messages ever encrypted for one secret key. DON’T USE IT UNLESS YOU ARE REALLY FORCED TO DO SO.

`--override-session-key `string``

  Don’t use the public key but the session key `string`. The format of this string is the same as the one printed by `--show-session-key`. This option is normally not used but comes handy in case someone forces you to reveal the content of an encrypted message; using this option you can do this without handing out the secret key.

`--ask-sig-expire`
`--no-ask-sig-expire`

  When making a data signature, prompt for an expiration time. If this option is not specified, the expiration time set via `--default-sig-expire` is used. `--no-ask-sig-expire` disables this option.

`--default-sig-expire`

  The default expiration time to use for signature expiration. Valid values are "0" for no expiration, a number followed by the letter d (for days), w (for weeks), m (for months), or y (for years) (for example "2m" for two months, or "5y" for five years), or an absolute date in the form YYYY-MM-DD. Defaults to "0".

`--ask-cert-expire`
`--no-ask-cert-expire`

  When making a key signature, prompt for an expiration time. If this option is not specified, the expiration time set via `--default-cert-expire` is used. `--no-ask-cert-expire` disables this option.

`--default-cert-expire`

  The default expiration time to use for key signature expiration. Valid values are "0" for no expiration, a number followed by the letter d (for days), w (for weeks), m (for months), or y (for years) (for example "2m" for two months, or "5y" for five years), or an absolute date in the form YYYY-MM-DD. Defaults to "0".

`--allow-secret-key-import`

  This is an obsolete option and is not used anywhere.

`--allow-multiple-messages`
`--no-allow-multiple-messages`

  Allow processing of multiple OpenPGP messages contained in a single file or stream. Some programs that call GPG are not prepared to deal with multiple messages being processed together, so this option defaults to no. Note that versions of GPG prior to 1.4.7 always allowed multiple messages.

  Warning: Do not use this option unless you need it as a temporary workaround!

`--enable-special-filenames`

  This options enables a mode in which filenames of the form `-&n`, where n is a non-negative decimal number, refer to the file descriptor n and not to a file with that name.

`--no-expensive-trust-checks`

  Experimental use only.

`--preserve-permissions`

  Don’t change the permissions of a secret keyring back to user read/write only. Use this option only if you really know what you are doing.

`--default-preference-list `string``

  Set the list of default preferences to `string`. This preference list is used for new keys and becomes the default for "setpref" in the edit menu.

`--default-keyserver-url `name``

  Set the default keyserver URL to `name`. This keyserver will be used as the keyserver URL when writing a new self-signature on a key, which includes key generation and changing preferences.

`--list-config`

  Display various internal configuration parameters of GnuPG. This option is intended for external programs that call GnuPG to perform tasks, and is thus not generally useful. See the file `doc/DETAILS` in the source distribution for the details of which configuration items may be listed. `--list-config` is only usable with `--with-colons` set.

`--gpgconf-list`

  This command is similar to `--list-config` but in general only internally used by the `gpgconf` tool.

`--gpgconf-test`

  This is more or less dummy action. However it parses the configuration file and returns with failure if the configuration file would prevent `gpg` from startup. Thus it may be used to run a syntax check on the configuration file.

#### Footnotes

### (1)

Using a little social engineering anyone who is able to decrypt the message can check whether one of the other recipients is the one he suspects.

Next: Deprecated Options, Previous: Compliance Options, Up: GPG Options [Contents][Index]